Molded ladder



April 9, 1957 H. E. MORRISON MOLDED LADDER Filed July 1:5, 1953 &

' INVENTOR. v Harald-E Huff/500..-

United States Patent MOLDED LADDER Harold E. Morrison, San Francisco,Calif., assignor of one-third to G. B. Haynes, Los Altos, and one-thirdto D. R. McNeill, In, San Francisco, Calif.

Application July 13, 1953, Serial No. 367,710

3 Claims. (Cl. 228-18) This invention relates to ladders and has for itsmain object the provision of a ladder that is very light in weight, yetstrong and rigid, and which ladder is molded or cast from electricalinsulation material.

Another object of the invention is the provision of a ladder adapted tobe formed in a single molding operation from a composition material suchas fiberglass and a suitable binder, and which ladder is so designed asto provide the maximum strength and maximum lightness in weight.

A still further object is the provision of an extension ladder that isvery strong, light in weight and in which the sections forming suchladder are substantially of the same structure and so constructed andassembled that one ladder section guides the other during extension orretraction of one section relative to the other.

The use of fiberglass and a plastic is not new in itself. Automobilebodies, furniture, and other articles have been molded from suchmaterial, which is extremely strong and very light in weight.

The present structure provides a ladder that is capable of being formedin one molding step, and the parts of the ladder are so designed as tonot only enable said molding operation, but to give maximum strengthwhere required, together with minimum material for such strength.Inasmuch as the finished ladder is an excellent non-condoctor ofelectricity, it is particularly suitable for linemen and for others thatmay find occasion to use the ladder where it would be dangerous to useladders of other material.

Other objects and advantages will appear in the description and in thedrawings.

In the drawings,

Fig. 1 is a fragmentary perspective view of a ladder made in accordancewith this invention and showing the structure that contributes to theemployment of the structure in making an extension ladder.

Fig. 2 is an enlarged sectional view taken along line 2-2 of Fig. 1.

Fig. 3 is an enlarged sectional view taken along line 3-3 of Fig. 1.

In detail, the side pieces of the ladder are generally designated 1, 2,and the rungs are designated 3. The side pieces and rungs are formedintegrally in one piece, and each side piece comprises a verticallyelongated channel member having sides 4, 5, and a curved bottom wall 6(Fig. 2

The remaining side is open and may be called the rear side since itwould face away from the user when the ladder is in use.

The sides 4, extend divergently relative to each other from bottom wall6, and their inner surfaces 7 are preferably flat. The sides 4, 5 areprogressively increasing in thickness along their free edges, as bestseen at 8 in Fig. 2, which increased thickness along said edges servesto strength the side pieces. Otherwise the thickness of the materialforming said sides is of uniform thickness, preferably of about onequarter of an inch, but this inice 2 vention is not restricted to suchthickness for the ladder may be made of any dimensions found mostdesirable for the jobs to be done.

Each of the rungs 3 is also a channel member. Said rungs have laterallyopening sides that are directed in the same direction as the open sidesof the vertically extending side pieces 1, 2 when the latter arevertical.

The upper side 10 of each rung slants slightly upwardly in a rearwarddirection (the rear side being the open side that is directed away fromthe user) and said side 10 'is of progressively increasing thickness insaid rearward direction.

The lower side 11 of each rung extends divergently relative to side 10in a rearward direction and bottom wall 12 is curved transversely of thelength of each rung and integrally joins sides 10, 11. Y

The side 11 of each rung curves downwardly (in a rearward direction)rather steeply from a point spaced slightly rearwardly of bottom wall12, thus producing a generally vertically extending marginal portion 13along the open side of each rung, which marginal portion acts like atruss for supporting weight in said rung.

The rungs 3 extend between the opposed sides 5 of side pieces 1, 2 andpositioned between the sides 4, 5 of each side piece at each end of eachrung is a web 15 (Fig. 2)

that joins the sides 4, 5 of each side piece to materially stiffen andstrengthen each of said side pieces.

Also, spaced along rungs 3 and between upper and lower sides 10, 11 ofeach rung are webs 16 integrally connecting said sides thus stiflieningthe rungs (Fig. 3).

The webs 15 that are between the sides 4, 5 of the side pieces 1, 2 arecurved along their rearwardly directed free edges at the open sides ofsaid side pieces, and as these webs are horizontal (when the side piecesare vertically extending), their curved rear edges extend horizontally.Said curved rear edges of the webs 15 substantially correspond to thehorizontal cross sectional contour of the outer side of the bottom wall6 of each side piece.

In an extension ladder, the upper section 20 (Fig. 1) and the lowersection 21, have paralleLside pieces of the same spacing and arepositioned so that the curved bottom wall 6 of the side pieces of thesection extend be tween the walls 4, 5 of the side pieces of the othersection and against the curved edges 17 of webs 15 thus said webs formguides slidably supporting the side pieces of one of the two sections.If it were not for said webs, the side pieces would jam one within theother, but with this structure they readily slide relative to eachother.

The conventional straps 25 (only two are shown, there usually beinganother set spaced from these along the ladders) hold the laddersections together. The usual supports in extension ladders (not shown)at the lower end of the upper one, serve to hold the upper ladder inextended position. No claim is made to such supports since they are oldand are readily adapted to the present ladders.

From the structure shown, it is not only apparent that the ladder can bereadily molded in one piece, but the structure that contributes to thatresult also contributes to strengthening the ladder and bracing the sidepieces and rungs against any tendency to twist or to bend when theladder is in use.

I claim:

1. In a ladder having elongated generally vertically extending sidepieces disposed in a common plane in side by side horizontally spacedrelation, vertically spaced rungs extending between and connecting saidside pieces, said rungs being in the form of horizontally extendingchannel members having an upper side wall and a lower side wall and abottom wall connecting them along one of their longitudinally extendingedges and the sides of said rungs opposite. their. bottom walls beingopen and generally directed perpendicular to said plane, the lower sideWall of each rung being curved downwardly in cross sectional contourtransversely of each rung and the upper side Wall of each rung. having asubstantially flat upper side extending slightly upwardly relative toahorizontal plane in direction toward its free edge when said side piecesare vertical.

2. An extension ladder comprising apair of ladder sections each having.a pair of elongated parallel side pieces equally spaced apart and withthe side pieces of one section aligned with those of the other sectionin direction transversely of said sections, each of said side piecesbeing in the form of a channel having generally opposed side Walls and abottom wall? connecting them along one of their free edges with theirside opposite said bottom wall being. open, the bottom walls of thesidepieces of one pair extending into the. open sides of the Side pieces ofthe other. pair, and means within the. said. side pieces of said otherpair slidably engaging the said bottom walls that extend into said opensides for sliding one of said ladder sections longitudinally thereofrelative to the other and means connecting said sections for holdingthem together during such sliding, the open sides ofthe side pieces ofsaid sections being directed laterally of the plane in which the sidepieces of each section are disposed.

3. An extension ladder comprising a pair of ladder sections each havinga pair of elongated parallel side pieces equally spaced apart and withthe side pieces of one section aligned with those of the other sectionin direction transversely of said sections, each of said side piecesbeing in the form of a channel having generally opposed side walls and abottom wall connecting them alongone of their free edges with their sideopposite said bottom wall being open, the bottom. walls of the sidepieces of one pair extending into the open sides of the side pieces ofthe other pair, and means within the said side pieces of said other pairslidably engaging the said bottom Walls that extend into said open sidesfor sliding one of said ladder sections longitudinally thereof relativeto the other and means connecting said sections for holding themtogether during such sliding,'saidmeans within. said side pieces beingwebs connecting the side walls of said last mentioned side piecesreinforcing the latter, the open sides of the side pieces of saidsections. being directed laterally of the plane in which the side piecesof each section are disposed.

References Cited in the file of this patent UNITED STATES PATENTS1,376,150 Miller Apr. 26, 1921 1,731,611 Clark Oct. 15, 1929 1,912,331Wikstrand May 31, 1933 2,064,803 Grove Dec. 15, 1936 2,127,035 KirlinAug. 16, 1938 2,237,329 Bischof Apr. 8, 1941 2,542,398 Crumpton Feb. 20,1951 2,550,274 Kuhler Apr. 24, 1951 2,588,959 Campbell Mar. 11, 19522,613,397 Borkland- Oct. 14, 1952

